Synthesis and Secondary Structure of cis-Stereoregular Poly(N-propargylcarbamates) Having Various Side Chains
journal contributionposted on 19.04.2005, 00:00 by Fumio Sanda, Shino Nishiura, Masashi Shiotsuki, Toshio Masuda
cis-Stereoregular poly(N-propargylcarbamates) [poly(1)−poly(6)] were synthesized by the polymerization of the corresponding monomers [1: (S)-CH⋮CCH2NHCOOCH(CH3)CH2CH3; 2: (S)-CH⋮CCH2NHCOOCH2CH(CH3)CH2CH3; 3: (S)-CH⋮CCH2NHCOOCH2CH2CH(CH3)CH2CH3; 4: (S)-CH⋮CCH2NHCOOCH2CH2CH2CH(CH3)CH2CH3; 5: (S)-CH⋮CCH2NHCOOCH(CH3)CH2CH2CH2CH2CH3; 6: (S)-CH⋮CCH2NHCOOCH(CH3)Ph] with a rhodium catalyst. Poly(2)−poly(6) took helical structure stabilized by intramolecular hydrogen bonding. They changed the conformation with temperature and addition of a polar solvent. Effects of the distance between the chiral center and main chain and the phenyl group were examined. 1H NMR and CD spectroscopic analyses revealed that the closer the distance between the chiral center and main chain, the more stable the helix and the rigid the polymer, i.e., poly(5) > poly(2) > poly(3) > poly(4). When the distance between the chiral center and main chain was the same, the polymer without phenyl groups [poly(5)] was more rigid than the one with phenyl groups [poly(6)], and the helical structure of the former was more stable.